Percussion tools



Nov. 28, 1961 J. K. HOLDO PERCUSSION TOOLS 5 Sheets-Sheet 2 Filed Jan.5, 1960 IIIIIIII/l/Y/IIIIIIII i la Nov. 28, 1961 JQK. HOLDO PERCUSSIONTOOLS Filed Jan. 5, 196 0 5 Sheets-Sheet 3 ATTORNEY NOV. 28, 1961 J, K,HQLDO 3,010,431

pERcussion TOOLS Filed Jan. 5, 1960 5 Sheets-Sheet 4 Fig. 5

9 9lcu INVENT BY a ATTORNEY Nov. 28, 1961 J. K. HOLDO PERCUSSION TOOLS 5Sheets-Sheet 5 Fig. 6

Filed Jan. 5, 1960 ":IVEN m W ,Z/LATTQRNEY United States Patent Ofitice3,010,431 Patented Nov. 28, 1961 3,010,431 PERCUSSION TOOLS Jan KristianHoldo, Stockholm, Sweden, assignor to Atlas Copco Aktiebolag, Nacka,Sweden, a corporation of Sweden Filed Jan. 5, 1960, Ser. No. 550 10Claims. (Cl. 121-36) This invention relates to improvements inpercussion tools having a housing, a working cylinder formed in saidhousing, and a hammer piston reciprocable in said working cylinder underthe action of a pressure fluid. The invention is particularly directedto portable percussion tools such as paving breakers, hammers, riveters,rock drills and the like but the invention may also be used in piledrivers, sheeting drivers or the like. piston in tools according to theinvention may be operated pneumatically or hydraulically or by otherpressure fluids as the case may be. A disadvantage of percussion toolsis the vibrations or shocks transmitted to the handles or other membersserving to feed or to carry the tool towards a work piece duringoperation of the tool. One object of the invention is to minimize oreliminate said shock and vibration transmission. A further object of theinvention is to provide a simple, economical and efiicient percussiontool in which the transmission of vibrations or shocks from the tool tothe handle or handles or other feeding means is materially reduced. Astill further object of the invention is to provide a tool in whichmechanical springs for cushioning of shocks or vibrations are avoided.Another object of the invention is a tool in which transmission ofvibrations and shocks to a handle or other member in which vibrationsare undesirable is eliminated or minimized irrespective of the forcewith which the operator presses the tool towards a work piece, such as astreet pavement. For the above and other purposes I provide pneumaticmeans for forming a force transmitting connection between a handle orother member in which vibration is undesirable and a percussion toolhaving a housing, a working cylinder in said housing, and a hammerpiston reciprocable in said working cylinder under the action of apressure fluid,

I provide in a tool of the type described servo motor:

means carried by the tool for operating pressure fluid supply controlmeans on the tool and manually operated means at the handle or othermember for actuating said servo motor means to operate the fluid supplycontrol means.

Further features of the invention will be apparent from the followingspecification and drawings which illustrate by way of example oneembodiment, and a modification thereof, of a percussion tool accordingto the invention.

The hammer However, other modifications of the invention may nat- Iurally be made within the scope of the appended claims. The hammerpiston of the tool may, for instance, be driven hydraulically in one orboth directions. The-hammer piston may also be steam driven.

The illustrated tool is a portable pneumatic concrete;

is a longitudinal section through the cylinder axis of the breakeraccording to FIG. 1 on a plane perpendicular to the section plane ofFIG. 2. FIG. 3 is a longitudinal section through the cylinder axis ofthe same tool on a plane at 45 to the section planes of FIGS. 1 and 2.FIG. 4 is a transverse section on line IVIV of FIG. 3. FIG. 4 alsoillustrates the planes II, IIII and IIIIII on which the longitudinalsections of FIGS. 1 to 3, respectively, are taken. FIGS. 5 and 6 arelongitudinal sec tions of a modification of the tool in FIGS. 1-4. FIG.7 is a cross section on line VIIVH of FIG. 6.

The tool illustrated in FIGS. 1 to 4 has a housing comprising a cylindercasing 1, a front casing 2, and a cylinder-head 3 which are boltedtogether by means of longitudinal bolts 4, 4 and nuts 5, 5. The cylindercasing 1 has a cylindrical bore 6 in which a hammer piston 7 isreciprocable and defines a rear chamber 8 and a front chamber 9. Thefront end of the bore of the cylinder casing 1 accommodates a guidemember 10 'for an anvil block 11 which transmits hammer blows to a steelshank 12. The shank 12 is guided in a bushing 13 fixed in the frontcasing 2 and retained in the tool by a steel retainer 14 of conventionaldesign which cooperates with a collar 15 on a steel '16, such as a spikefor breaking concrete or asphalt pavement or the like. The steelretainer 14 permits removal of the steel 16 and is in all respectsconstructed in conventional manner and is therefore not described indetail. The anvil block 11 has the usual collar 17 for limiting axialmovement of the anvil block.

At the rear end of the tool a handle member 18 is pro vided whichcarries two handles 19, 19 and forms a cap which fits the outside of thecylinder casing 1 with a sliding fit. The handle member 18 has securedthereto piston rods 20 which are rigidly secured to the handle member bynuts 21 and which are slidably guided in bushngs 22 in the casing v1 andcarry pistons 23 reciprocable 1n bores 24 in the cylinder casing 1. Thepistons are sealed in the bores by means of sealing rings 25. The twopistons 23 are movable in the bores 24 a limited distance and provide aforce connection between the handle member 18 and the tool which permitsaxial longitudinal relative movement of the tool and the handle member18 within certain limits.

The cylinder casing 1 carries a distributing valve casing 26accommodating a tubular air distributing valve 27 moveablelongitudinally of the tool in valve guides 28, 29 and illustrated inFIG.3 in a position in which compressed air admission to the rear chamber 8is closed and said chamber is connected to the atmosphere. Compressedair is supplied to the tool through a hose 30, a mam valve casing 31, apassage 32 in the main valve casing, a passage 33 in the distributingvalve casing and in open position of the distributing valve 27 through apassage 34 to the rear working chamber 8 in the cylinder casing 1.Compressed air is also supplied from the passage 32 through a conduit 35and a passage 36 in the casing 1 over a pressure reduction valve 37,actuated by a spring 38 through a passage 39 to a chamber 40 in thefront casing 2. The spring 38 is so dimensioned that the pressure in thechamber 40'may be kept. at a low value, for instance at a fewhec-tograms per square centimeter. The comparatively large chamber 40communicates through a passage 41 with the front chamber 9 in theworking cylinder. Instead of the pressure reduction valve 37 a constantpressure valve of conventional design may naturally be provided.

The main valve casing 31 accommodates a servo motor operated valvemember 42 which is provided with a piston portion 43 reciprocable in abore 44 in the main valve casing 31'. The bore 44 is closed by a cover45 to form a working chamber 57 for the piston portion 43. The annularspace 58 at the lower side of the piston portion 43 is vented to theatmosphere through closes. the valve 42.

a'passage 46. A hose 47 is secured. to a nipple 48 formed by the cover45 and leads to a valve chamber 49 formed in the handle member 18. Thechamber 49 accommodates a small poppet valve 50 which is normally keptclosed by a spring 51 provided between the valve head and a plug 52. Theplug 52 has a bore 53 forming a communication between the chamber 49 andthe atmosphere in open position of the valve member 50. The handlemember carries a trigger 54, which is journaled on a pin 55, andcooperates with the stem 56 of the poppet valve 50 so that thepoppetvalve may be opened against the pressure of the spring 51 by pressingthe trigger 54 towards the handle 19. The valve 42 has a fine passage 82through which compressed air in inoperative position of the tool isadmitted to the chamber 57. When the tool is at rest air pressure in thechamber 57 keeps the valve 42 closed since the annular chamber 58 isvented to the atmosphere through passage 46. When the trigger 54'ispressed the pressure air is vented from the chamber 57 and the airpressure in the supply hose 30 then opens the valve 42 to admitcompressed air to the passages 32, 33, 34. As soon as the pressure onthe trigger 54 is released the poppet valve 50 closes the vent passagefrom the chamber 49 so. that air pressure again builds 1 up in thechamber 57 and Compressed air admitted to the passages 32, 33 flows inthe illustrated position of the distributing valve 27 through a passage60 to an annular space 61 in which it acts on the shoulder 62 of thedistributing valve 27. The air pressure which builds up in the chamber40'as soon as the trigger 54 has been pressed down lifts the piston 7 tothe top of the bore 6 causing compression of the air in the rear portionof the working chamber 8. Compressed air from the rear portion of thechamber 8 is conducted through a passage 63 to an annular space 64 inwhich it acts on a flange 65 'on the distributing valve 27 so that saidvalve is moved to the lower position in which it admits air to the rearworking chamber 8 in the cylinder afterthe rebound of the piston againstthe air cushion at the upper end of the'chamber '8. The compressed airadmitted to the chamber 8 drives the piston 7 downwardly against theanvil-block '11 and when the piston on its working stroke has uncovereda passage 66 in the wall of the cylinder 1 compressed air from thechamber 8 is con ducted through the passage 66 to an annular chamber 69in which it actuates the distributing valve member 27 upwardly in FIG.3-so that the admission of compressed air to the chamber 8 is closed'andan exhaust passage from the chamber 8 is opened through the passage 34and the interior 70 of the valve member and further through a passage 71to the atmosphere. Two chambers 72 with several times as great volume aschamhere 73 confined in the bores 24 by the two pistons 23 are providedin the casing 1. Preferably the volumes of the chambers 72 and bores 24may be between ZOand 30 times the volumes displaced by thepistons 23during 7 7 operation of the tool so that displacements of the pistons 23in the bores 24' do not materially change the pressurein the chambers 72which are interconnected by a 'large passage 74 and connected to thebores 24 by large 7 The annular chambers on the rear side of passages75. V the pistons 23 are vented to theratmo'sphere through passages 80.As soon as the tool is connected to a compressed air s'upply sourcethrough the hose 300cmpressed air is conducted through a hose or conduit76 a to the chambers 72 at 77 in FIGS. '3 and 4. The passage into thechamber 72 goes through a fine bore 78 and the chambers 73 'areprovided-with openings leading to the atmosphere and controlled by thepistons 23, said openings being considerably larger than the bore 78 sothat low air'pressure only, tor instance about one kilogramme per squarecentimeter above atmospheric pressure, can be built up in the workingchambers 73 when the openings 79 are uncovered by the pistons 23.

4 In order to adjust the pressure in the chambers 72 adjusting screws 81are provided.

The described tool operates in the following manner: It will beunderstood that as soon as the operator holding the tool by means of thehandles 19 presses the trigger 54 air pressure on the servomotor piston43 in the chamber 57 is reduced so that air pressure in the hose 30opens the main valve 42. Compressed air is then admitted to the valvecasing 26 and the chamber 40. The only force acting in longitudinaldirection of the tool on the handles 19 is then the air pressure in thechambers 73 which tends to lift the pistons 23 in the bores 24. The rearside or the pistons 23 being continuously vented to the atmospherethrough the passages in the piston rods 20. When the operator pressesharder on the handles 19, pressure in the chambers 73 is graduallyincreased but during operation with the operator pressing the handleswith the same force the pressure in the chambers 73 will remainsubstantially constant and said pressure will remain constantirrespective of the vibrations in'axial direction set up in thetoolduring the hammer reciprocation. It will be observed that a movement ofthe cylinder casing 1 towards the handles 19 causes the pistons 23 to.momentarily close the openings 79 but due to the small size of thepassage 78 and the size of the displacement volume of the pistons 23relative to the cylinder chambers 72 and 73 no ap preciable increase inpressure in the chambers 73 occurs during such intervals so that noshock will be transmitted to the handles 19. The same applies if thecasing 1 from the position illustrated in FIG. 1 moves downwardly awayfrom the handles in which case the ports 79 are uncovered so that partof the air in the chambers 72 may escape. The area of the openings 79 isso small that air losses during these intervals of normal oscillation ofthe housing relative to the handle member are comparatively small and inthe present tool the extra air consumption for vibration dampeningpurposes is therefore small. The air losses are naturally compensated bythe air supply through the small passage 78 so that an equilibrium ismaintained. It has been found that the area of openings 79 may be 10 to20 times the area of passage 78. The arrangement works to minimizetransmission of vibrations from the tool to the handles on idle runningof the tool as well as when the operator presses the handles and thetool more or less towards the ground or the like and the handle membertakes a mean position relative'to'the housing which moves only a smalldistance under various forces applied by the operator. V

The tool above described should be considered only as an example and maybe modified in various ways within the scope of the claims. In cases,for instance, where it is not necessary to be able to turn the tool onthe cylinder axis by means of the handle or handles a single piston andcylinder concentric with the Working cylinder may replace the pistons 23and cylinders 24.

The illustrated distributing valve 27 may be replaced by a conventionalvalve which controls the pressure fluid supply to the rear chamber 8 andthe front chamber 9, and such avalve may also control the exhaust fromsaid chambers.- The illustrated servo control of the main valve 42 maybe replaced by electric control or me chanical linkage which do nottransmit vibrations from the tool to the handle member. in themodification illustrated in FIGS. 5, 6 and 7 parts corresponding toequivalent parts in FIGS. 1 to 4 are designated .with the same referencenumerals and are not described again. The main difference between thetools illustrated in FIGS. 5-7 and the above described tool is asfollows:

The damper pistons 23in FIGS. 5 and 6 are provided on piston rods 83which are not connected to the handle member 18 but 'are only pressedagainst the inside of said 'member'with their rear ends which in orderto avoid metallic contact are provided with rubber caps 83a. The

air pressure in the chambers 73 keeps the rods 83 pressed towards thehandle member 18 as soon as the tool is connected to a compressed airsource. The guiding function of the piston rods 20 in FIG. 1 isperformed by separate guide rods 84, secured to the handle member 18 bymeans of nuts 85 and guided in bushings 87 and provided with heads 88 attheir front ends. The tube 47 from the trigger control valve 50 has beenreplaced by a passage 89 and a telescopic tube 90 secured to the handlemember 18 and movable in a bore 91 in the casing 1 and providing acommunication, via port passage 91a and an external annular groove inthe plug 91b, with the chamber 57 at the large end of the main valve 43.The tube 90 communicates with the bore 91 through openings 92 which areso positioned that when the tool is lifted by means of the handle member18 the openings 92 are closed by a bushing 93 causing the hammer pistonto stop its reciprocation.

The distribution valve 27 of the tool in FIGS. and 6 is of a type whichcontrols the air supply to the rear chamber 8 as well as to the frontchamber 9 of the tool and also auxiliary exhaust passages from the frontand rear chambers. The valve 27 is a piston valve which is moved axiallyby compressed air admitted to the rear and front ends of the valve, whenthe hammer piston uncovers a passage 94 or a passage 95, respectively.

Compressed air from the main valve is supplied to the annular chamber 96and in the upper position of the piston valve 27 through a number ofopenings 97 to the rear chamber 8 and in the lower position of thepiston valve 27 through the annular recess 98 and the passage 99 to thefront chamber 9. 100 is a vent passage, which in the lower position ofthe piston valve 27 permits the air from a part of the air cushion inthe chamber 8 to escape slowly to the atmosphere during the returnstroke of the hammer piston 7 so that a reduced or non-cushioningefl'ect is obtained in the chamber 8 on the return stroke of the hammerpiston 7. 101 is a vent passage which in similar manner brings thechamber 9 in communication with the atmosphere in the upper position ofthe piston valve 27 so that the air compression in the chamber 9 isreduced or avoided until the hammer piston has delivered the blow. Thefinal exhaust of the air in the chambers 8 and 9 is controlled inconventional manner by the hammer piston 7 which on the working strokeuncovers a groove 102 and on the return stroke a groove 103 whichgrooves are connected with conventional exhaust ports (not shown). Thechamber 9 is connected through a passage 104 to a space 165 forming anair magazine communicating with the chamber 9.

The reduction or elimination of vibrations transmitted from the housingof the tool in FIGS. 5-7 operates in the same way as in the embodimentof the invention disclosed in FIGS. 1-4'and is consequently notdescribed again.

What I claim is: I

1. In combination with a percussion tool having a housing, a workingcylinder formed in said housing, and a hammer piston reciprocable insaid working cylinder under the action of a pressure fluid, a member inwhich vibration is undesirable, pneumatic means for transmitting forcebetween said member and said housing, and means operative to effectpneumatic control of said first mentioned means for automaticallyadjusting the value of said force to maintain said member relative tosaid housing in a substantially predetermined means position and formaintaining such adjusted value relatively constant over a considerablenumber of successive reciprocations of said hammer piston.

2. In combination with a percussion tool having a housing, a workingcylinder formed in said housing, and a hammer piston reciprocable insaid working cylinder under the action of a pressure fluid, a member inwhich vibration is undesirable, pneumatic piston and cylinder means fortransmitting force between said memberand said housing, one of saidmeans being carried by the member and the other means by the housing,means for guiding said member relative to said housing for motion in thedirection of the axis of the working cylinder, and means operative toeffect pneumatic control of said first mentioned means for automaticallyadjusting the value of said force to maintain said member relative tosaid housing in a substantially predetermined mean position and formaintaining such adjusted value relatively constant over a considerablenumber of successive reciprocations of said hammer piston.

3. In combination with a percussion tool having a housing, a workingcylinder formed in said housing, and a hammer piston reciprocable insaid working cylinder under the action of a pressure fluid, a member inwhich vibration is undesirable, pneumatic piston and cylinder means fortransmitting force between said member and said housing, one of saidmeans being carried by the member and the other means by the housing,means for guiding said member relative to said housing for motion in thedirection of the axis of the working cylinder, a damper working chamberin said cylinder means having a compressed air inlet opening and acompressed air outlet opening, said outlet opening having greater areathan said inlet opening, and said piston means cooperating with saidoutlet opening to control and maintain in said damper chamber asubstantially constant pressure during successive hammer pistonreciprocations.

4. A percussion tool according to claim 3, in which said damper chambercontinuously communicates with an air magazine chamber.

5. In combination with a percussion tool, having a housing, a workingcylinder formed in said housing, a hammer piston reciprocable in saidworking cylinder under the action of a pressure fluid, means in thehousing for supplying pressure fluid to the working cylinder, means inthe housing for leading fluid away from the working cylinder, and meansassociated with the housing for controlling the supply ofpressure fluidto the working cylinder, a member in which vibration is undesirable,means for forming a connection between said member and said toolproviding limited relative sliding motion in the direction of the axisof the working cylinder between said member and said tool, cooperatingdamper cylinder and piston means for transmitting force in the directionof said axis from said member to said tool, a damper working chamber insaid damper cylinder means having a compressed air inlet opening and acompressed air outlet opening, said outlet opening having greater areathan said inlet opening.

6. In combination with a percussion tool, having a cylinder housing, aworking cylinder formed in said housing, a hammer piston reciprocable insaid working cylinder under the action of a pressure fluid, means in thehousing for supplying pressure fluid to the working cylinder, means inthe housing for leading working fluid away from the working cylinder,means carried by the housing for controlling the supply of pressurefluid to the working cylinder, a handle member for holding and directingsaid tool, means for forming a connection between said handle member andsaid tool providing limited relative sliding motion in the direction ofthe axis of the working cylinder between said handle member and saidtool, servomotor means carried by the housing for operating said supplycontrol means, and manually operable means at said handle member foractuating said servomotor means to open the supply control means.

7. In combination with a percussion tool, having a housing, a workingcylinder formed in said housing, a hammer piston reciprocable in saidworking cylinder under the action of a pressure fluid, means in thehousing 7 for supplying pressure fluid to the working cylinder, means inthe housing for leading working fluid away from the workingcylinder, andmeans carried by the housing for controlling the supply of pressurefluid to the working cylinder, a handle member for holding and directingsaid tool, means for transmitting force between said handle member andsaid housing, means for autornatically adjusting the value of said forceto maintain said handle member relative to said housing in asubstantially predetermined mean position and for maintainin-g suchadjusted value relatively constant over a considerable number ofsuccessive reciprocations of said hammer piston, servomotortmeanscarried by the housing for operating said supply control means andmanually operable means at said handle member for actuating saidservomotor means to open the supply control means.

8. In combination with a percussion tool having a housing, a workingcylinder formed in said housing, a

, hammer piston reciprocable in said working cylinder member and saidhousing, means operative to effect pneumatic control of said firstmentioned means for automatically adjusting the value of said force tomaintain said member relative to said housing in a substantiallypredetermined mean position -and for maintaining such adjusted valuerelatively constant over a considerable number of successivereciprocations of said hammer piston, means in the housing for supplyingpressure fluid to the working cylinder, distributing valve means in thehousing controlling pressure fluid supply to working chambers in theworking cylinder for producing a rapid working stroke and a relativelyslow return stroke and including a distributing valve member, passagesin said distributing valve means for venting the main portion of thecompressed air cushions produced by the hammer piston during the workingstroke and the return stroke, respec: tively, and further passages inthe distributing valve means for supplying pressure fluid for movingsaid distributing valve member to positions for admitting pressure fluidto said working chambers, respectively.

9. In combination with a percussion tool, having a housing, a workingcylinder formed in said housing, a hammer piston reciprocable in saidworking cylinder under the action of a pressure fluid, a handle memberslidable in the direction of the axis of the working cylinder a limiteddistance relative to said housing and nonrotatable relative to thehousing, two damper cylinders in the housing parallel with the workingcylinder, damper pistons and piston rods movable in said dampercylinders and engaging said handle member to move the handle member awayfrom the housing under the action of compressed air supplied to thedamper cylinders, guide rods connected to said handle member and guidedin the housing to allow the handle member to move a limited distancealong the axis of the working cylinder relative to the housing,auxiliary compressed air chambers in the 7 housing communicating withdamper chambers in said damper cylinders, a compressed air inlet openingineach damper chamber, a compressed air outlet opening in each damperchamber having greater area than said inlet'opening and controlled bysaid damper piston, respectively, means in the housing for supplyingpressure fluid to the working cylinder, and servomotor means controlledfrom the handle member for controlling the pressure fluid supply means.

10. A percussion tool according to claim 9 in which servo motor meansincludes a telescopic connection between the handle member and thehousing operable to interrupt pressure fluid supply to the workingcylinder when the tool is lifted by means of the handle member.

References Cited in the file of this patent UNITED STATES PATENTSAltschuler June 5, 1956

